Hi,
Indeed the options you specified:
-DPYTHON_EXECUTABLE=/usr/bin/python3 -DPYTHON_INCLUDE_DIR=/use/include/python3.6m -DPYTHON_LIBRARY=/usr/lib/x86_64-linux-gnu/libpython3.6m.so.1
should be enough to make it point to the right Python installation. Can you try the three options again from scratch, in a clean build?